1. Field of the Invention
This invention relates generally to telecommunications. More particularly, it relates to location based services (LBS) and wireless emergency services such as E911, and short messaging system (SMS) messaging.
2. Background of the Related Art
9-1-1 is a phone number widely recognized in North America as an emergency phone number that is used to contact emergency dispatch personnel. Enhanced 9-1-1 (E9-1-1) is defined by an emergency call being selectively routed to an appropriate PSAP, based on a special identifier (P-ANI, or “Pseudo Automatic Number Identifier”, also referred to as “ESxK”), and includes the transmission of callback number and location information when 9-1-1 is used. E9-1-1 may be implemented for landline, cellular or VoIP networks. A Public Service Answering Point (PSAP) is a dispatch office that receives 9-1-1 calls from the public. A PSAP may be a local, fire or police department, an ambulance service or a regional office covering all services. As used herein, the term “PSAP” refers to either a public safety access point (PSAP), or to an Emergency Call Center (ECC), a VoIP term.
Regardless of the network type, a 9-1-1 service becomes E-9-1-1 when automatic number identification and automatic location information related to the call is provided to the 9-1-1 operator at the PSAP. A primary challenge results from the fact that calls may arrive at the PSAP without the caller's actual callback number or location information displayed at the emergency operator's terminal.
The current 911 infrastructure is designed to route a live voice call to a local public safety answering point (PSAP). This requires that voice circuits be available. The result of an E911 call is a direct circuit switched voice connection between an emergency service requester and a suitable responder. 911 is further enhanced with the ability to deliver location over a data channel in parallel to the call. The location data is typically staged in a database that is queried by the PSAP to determine location information.
FIG. 7 shows a conventional landline public safety access point (PSAP) to automatic location identifier (ALI) connection.
In particular, FIG. 7 shows a PSAP 400 connected to one Automatic Location Identifier (ALI) database 401. Upon receiving a 9-1-1 call, the PSAP 400 queries the ALI 401 for location data. The ALI database 401 accepts the query from the PSAP 400 for location. The query includes the telephone number of an emergency caller. The ALI database 401 relates the received telephone number to a physical street address and provides that street address (location information) back to the PSAP 400 in a manner that works for the customer premise equipment (CPE) display at the PSAP 400.
An ALI is typically owned by a local exchange carrier (LEC) or a PSAP, and may be regional (i.e. connected to many PSAPs) or standalone (i.e. connected to only one PSAP). There is currently no one single standard interface protocol for PSAP-ALI connection/communication.
FIG. 8 shows a context diagram for a conventional non-landline positioning center (e.g., an Internet based voice over Internet Protocol (VoIP) positioning center).
In particular, the ALI database 401 includes a conventional emergency services key (ESQK or ESRK) in a location request sent to an appropriate positioning center 402 (XPC). The emergency services key (ESQK or ESRK) is used by the positioning center 402 as a key to look up the location and other call information associated with the emergency call.
In non-landline telephony, the PSAPs 400 query the ALI 401 for location information. However, the ALI 401 is not pre-provisioned with location data for non-landline calls (e.g. cellular, VoIP etc) and must communicate with other network entities to obtain and deliver location data to the PSAP 400.
Non-landline telephony standards (e.g. cellular, VoIP etc) have mandated that ALIs 401 maintain connectivity to a positioning center 402 that is able to provide current location data for a non-landline call. In the current state of technology, the positioning center 402 provides the caller's location and the callback number to the ALI, which passes it to the requesting PSAP. As can be seen in FIG. 8, an ALI may maintain connectivity to more than one positioning center via multiple interface types—both standard and non-standard (e.g. NENA-02, E2/E2+N-E2(ESP), PAM, etc.).
As used herein, the generic term “XPC” refers interchangeably to any standards-based positioning center. As examples, a positioning center 402 may be any one of the following types used in non-landline networks:                GMLC (Gateway Mobile Location Center): The positioning center that retrieves, forwards, stores and controls emergency position data within the GSM location network.        MPC (Mobile Position Center): The positioning center that retrieves, forwards, stores and controls emergency position data within the ANSI location network.        VPC (VoIP Positioning Center): The positioning center which retrieves, forwards, stores and controls emergency position data within the VoIP location network.        
The term “XPC network” is used herein when appropriate to refer to any non-landline network where a positioning center 402 responds to ALI queries including an emergency services key for location, e.g., cellular, VoIP etc.
911 calls require voice circuits to be available to complete the voice call to a PSAP. For the most part, PSAPs are capable of receiving only voice calls. Connectivity with a PSAP, established either through the existing time division multiplexed (TDM)-based emergency services network (ESN), or directly over the public switched telephone network (PSTN) to the PSAP, is managed through dedicated telephone switches that cannot be directly dialed.
The present inventors have appreciated that during times of regional crises, such as during a hurricane, the local wireless infrastructure can become overloaded by call volume. This was experienced during the Sep. 11, 2001, terrorist attacks during which voice telecommunications along the east coast was subjected to service failures.
There is a long-felt need for improving emergency communications to provide a system that is more rugged and reliable during times of regional crisis.